TDI

• Tolerable daily intake, in toxicology
• Toluene diisocyanate, an organic chemical
• Time delay and integration, timing synchronization in an image sensor
• Tissue Doppler imaging, a medical ultrasound technology
• Tabbed document interface, a type of graphical user interface
• Total dual integrality, a property of matrices in mathematical optimization
• Transport Driver Interface, used by NT series Windows to abstract level 7 APIs into a common protocol for the Transport Protocol layer
• Trophic Diatom Index, water quality and ecological status; see Sattal
• TDI (engine) (turbocharged direct injection), a diesel engine design used in cars and light vans made by Volkswagen Group

• Technical Diving International, a technical diving organization
• Telecommunications for the Deaf, Inc., a nonprofit organization promoting telecommunications devices for the deaf
• Texas Department of Insurance
• The Dartmouth Institute for Health Policy and Clinical Practice, a subsidiary of Dartmouth College
• Transportation Displays, Inc., a unit of Outfront Media
• Technical group of Independents (1999-2001)
• Technical group of Independents (1979-1984)

• Total Drama Island, an animated reality series
• Total Drama Island (2023), the 2023 reboot with the same name.
• Tangerine Dream Independent, the record label belonging to Edgar Froese

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